Centrifugal fan and pump.



S. C. DAVIDSON. CENTRIFUGAL FAN AND PUMP.

APPLICATION FILED SEPT-25. I912- Patented Aug. 10, 1915.

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APPLICATION FILED SEPT 25 I912 I Patented Aug. 10, 1915.

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S. C. DAVIDSON. CENTRIFUGAL FAN AND PUMP.

Paftented Aug. 10, 1915.

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SAMUEL oLEL'AND DAVIDSON, or BELFAST, IRELAND.

CENTRIFUGAL FAN- AND PUMP.

To all whom it may concern i Be it known that I, SAMUEL CLELAND DAVIDSON, of Sirocco Engineering Works, Belfast, Ireland, have invented certain new and useful Improvements in or Relating to Centrifugal Fans and Pumps, of which the following is a specification.

My invention has reference to centrifugal fans and pumps (which are hereinafter included in the term fans wherein the fluid dealt with (whether gaseous or liquid,

both of which are included in the term air) enters axially and is discharged circumferentially.

.My invention is applicable to fans-furnished with a fan wheel of the drum type, such as described in my prior Patent No. 662395, but the phenomena to which I'p'roceed to call attention existin other types of fans and so far as this is the case the prin ciple ofmy invention is applicable to such other fans.

Referring to the drawings :Figures 1 and 2 are vertical sections respectively of a single and a double inlet fan of known construction, the casings being omitted; Fig. 3 is a similar view of a single inlet fan, the front casing wall being shown; Figs. 4, 5, 6, 7, 8

and 9 are views similar to Figs. 1 and 2, illustrating various embodiments of the present invention, Figs. 10 and 11 are plan views showing the arrangement of. the guide blades; Fig. 12, is a sectional view showing a modified arrangement of the guide blades; Figs. 13 and l l are sectional views showing the present invention as applied to wall fans; Figs. 15 and 16 are respectively vertical section and side elevation of the invention as applied to an incased fan; Fig. 17 is a sectional elevation of amodified construction of incased fan; Figs. 18, 19 and 20 are respectively vertical section, side elevation and plan of a modified construction of single inlet wall fan; Fig. 21 is a View similar to Fig;

18 showing a double inlet fan; Figs. 22 and 23 are modifications of a conica fan shown in vertical section; Fig. 24 is a vertical elevation; chiefly in section, of a wall fan embodying the invention and applied to a ventilator; Figs. 25 and 26 show in sectional elevation and side view respectively a modification of the construction shown in Fig. 11; Figs. 27 and 28 are respectively sectional elevation-and side View of an iiicased fan employing guide vanes; Fig. 29 isa sectional Specification of Letters Patent. Patented Aug. 10, 1915.- Application filed September 25, i912. Serial No. 722,220.

tips of the blades in an even manner along their entire axial length. If-for example, a fan wheel which is open to the air at one end only, as indicated in Fig. '1, be rotated in the open without an inclosing casing of any sort, the outward discharge of air is always strongest from the end of the fan wheel which 18. completely closed (hereinafter called the back end) as indicated by arrows a a. The strength of this centrifugal discharge gradually diminishes and becomes practically ml at a point 0 about midway therefrom toward the intake end of the blades, and. from this point the current through the blades gradually assumes a cen axial inflow of air as indicated by arrow 0 into the interior of the fan wheel (hereinafter called the intake chamber).

In the case of a fan wheel of the double intake type, as shown in Fig. 2, where the fluid enters at both of the opposite-intake ends thereof, and whether the blades em:

ployed therein are mounted on each side of a disk, midway between the two oposite intake ends, or carried by centrally" located spokes or arms, suitably mounted or keyed on to the driving shaft, then that half, 01

thereabout, of the total axial length of the blades which is midway between, and

equally distant from, both intake ends of the fanwheel, discharges the fiuid'centrifugally outward, as indicated by the arrows a a and an inward centripetal flow exists, as indicated by arrows b and b at the two opposite intake ends of the blades iii the same manner as already described in respect of the single intake fan wheel shown in Fig. 1,

and there will be two neutral points 0 0 each at about one-quarter of the total axial length of the blades from each of the intake ends. When the fan wheel is rotated within a casing of the usual form, with a plate L forming one side of the casing with an eye as indicated in Fig. 3, the stream lines of the air flow much the same. a To find the direction of the stream line in any case at any particular point I have generally used streamers of thread or other suitable material attached to the end of a wire (hereinafter referred to as current indicators). My investigations have shown that these phenomena take place with very different forms and constructions of centrifugal fan wheels in which air. enters axially and is discharged circumferentially, and with many difierent forms and arrangements of the blades therein. In particular I have found that the length or shortness of the blades in an axial direction and the sloping of the external or internal edge of the blade to the axis or having the blades arranged obliquely to the axis or' of a hyperboloid formation do not within wide limits substantially alter or affect the above phenomena, there being still in most cases a cen tripetal flow acting through the part of the blades which is nearest the intake end of the fan wheel (hereinafter for conciseness of description referred to as the negative part or end of the blade or of the fan wheel) combined with the centrifugal discharge from the part thereof farthest from the said intake end (hereinafter referred to as the positive part or end of the blade or of the fan wheel). I have found that the phenomena occur with fan wheels of what are ordinarily known as the paddle wheel type, having radially deep blades comparatively few in number, and also with fan wheels of the type known as multibladed, or drum construction, with radially shallow and numerous blades or with corrugated blades and also with a drum consisting of a cellular or honeycomb structure around the circumference of the wheel operating like blades- In.

fact my observations have shown that these phenomena only cease when the eye or inlet opening to the fan wheel is closed to a considerable extent from the circumference invward, or when the axial length of blade at the periphery is much less than the axial length at or near the hub, and the sides of the blades are shrouded, both of which condeal with these phenomena I have made many experiments with many different types of fans extending over several years, and in the course of these experiments have applied for patents for inventions dealing in a more or less incomplete manner therewith, viz: Nos. 801,303 and 820,398. By my present invention I am enabled to utilize these phenomena in such a way as to obtain greatly improved results.

According to my present invention I so arrange the fan wheel in relation to the case or other space in which it rotates that the air which passes through the negative portion of the blades is mainly taken from the suction or intake side of the fan (instead of being to a considerable extent a recirculation back from the discharge side), and so that the air thus entering centripetally through the negative end of the blades or passing axially between or along the same is discharged centrifugally through or from the positive portion of the blades. I

secure this result by means 'of a partitional device located relative to the periphery of the fan wheel and which substantially restricts the air passing centripetally through and axially along the negative portions of the blades to that mainly taken from the suction or intake end of the fan and which opposes the tendency of the air discharged through the positive ends of the blades to recirculate to the negative ends. This partitional device may have numerous forms: Among those illustrated are by dividing the space outside the periphery of the fan wheel by a partition located near the neutral point of the blades, or by a suitable form of eye which may be furnished with guide plates or by a combination of partition with guide blades or by locating the fan within a duct which is of such greater diameter than the fan Wheel that a substantial space is left between the periphery of the fan wheel and the said duct, and said duct may be furnished with guide blades extending over the negatiy e portion of the blades. In each case both sides of the negative portion of the blades rotate in the fluid which isentering on the suction side of the fan and has not yet passed through the positive part of the blades. Under such circumstancesI am also enabled by a suitable enlargement of the eye of the fan casing or of the space or suction duct in which the fan rotates to obtain a flow of air direct from the suction side of the fan into the discharge side of the fan without such air passing through the blades at all. To assist this induced flow of air suitable guide plates are or may be placed in the eye or in the space surrounding the fan wheel.

In my improved fan the air which comes through the negative portion of the blades centripetally or axially along their outer circumference, is drawn from the outer air and thus swells the volume entering the eye axially, instead of being taken as heretofore by recirculation from the volume of air which has already passed through the-posi tive portion of the blades. abled to prevent to a great extent the churning of air which has heretofore taken place, when a portion of the air which has passed through the positive portion of the blades is again passed through the negative portion to be again passed through the positive portion. Thus the intake of air is now not only axial but partly circumferential and centripetal, and in some cases a portion of the air is taken in by induction without passing through the fan wheel.

Fig. 4 illustrates the effect of a partition or dividing plate 2 (which may form the side of the fan casing or the wall or side of a compartment into which the discharge takes place) applied in accordance with my invention at or near the neutral point 0 of the blades instead of near the intake ends thereof as shown in Fig. 3. \Vith the arrangement inFig. 4 on applying the current indicator, it will be found that on the suction side of the plate 2 the already described .axial flow 0 through the intake opening of the fan wheel exists, and conjointly therewith a centripetal flow, also from the outer air onsuction side of the plate 2, as indicated by arrows I), through the spaces between the projecting ends of the blades. I On examining the currents on the other side of the dividing plate 2, the current indicator shows that although theoutward current is comparatively weak close to the dividing plate 2', this portion of the axial length of the blades is now discharging outwardly throughout its length, as indicated by arrows a.- v

lVith a double intake fan, as shown in Fig. 5, the arrangement for each half of the fan is similar to that indicated in Fig. 4. The air now enters at both intake ends of the fan wheel, the centrifugal discharge is from that portion of the axiallength of the blades which is centrally located between the two intake ends, and which therefore constitutes the positive part thereof, thus leaving the centripetally acting or negative portions at each end extending for about one-quarter of the axial length from each of the two intake ends of the blades. On rotating the fan wheel and applying the current indicator, there will be found at each of the opposite intake ends an axial flow 0 into the center of the fan wheel, and the inward or centripetal How I) b will be found from the outer circumference of the charge a a will be between the plates 2. a.

I am thus enor may form the termination may extend in one length from one intake end to the other, and be centrally supported by arms or spokes, or they may be mounted on spokes at each end, with or without a central disk or spokes and the same phenomena exist. Thus by the use of a partition or partitions such as 2 .2 according to my invention I obtain a centrifugal fan in which the contrary currents atthe negative and positive portions of the fan blades have been separated and utilized so as to work in unison one with the other, and in combination with the ordinary axial inflow.

In applying my invention to a single intake fan wheel such as is indicated in Fig. 1, I have employed a side wall of the casing as the partitional device. As shown in Fig. 4, the negative end of the fan wheel is arranged to protrude outward beyond the side of the casing for the required distance so that the side wall of the casing may fulfil the oilice of the before-mentioned partition z or, in the alternative, the side wall of the casing on the inlet side may be recessed inward around the intake side of the fan wheel as shown in Fig. 6, leaving the blades projecting outward from the casing for the required distance. Either way the casing acts as the before-described partition 2. The negative end of the fan wheel will thus protrude outward from the casing when the casing is recessed, therecess as illustrated in Fig. 6 fiares outwardly so that its outward diameter is larger than the fan wheel, while its inner termination is only slightly larger but said recess may be varied in form and dimensions to suit requirements and may either be freely open to the atmosphere,

7 of a duct leading up to the fan. a

.In the construction shown in Fig. 6, the casing is recessed around the eye, and the area for entry of air through the blades into the casing is reduced. The sectional area of the air passage through the casing should be substantially undiminished or even increased so as to provide for the same or an increased flow of air notwithstanding the diminution of the area 'of entry through the blades as illustrated in Fig. 6. A fan thus constructed according to my invention is specially applicable for compounding in series. To prevent any undue rotation of air being established outside the circumfer- 'ence of the projecting negative end of the blades, when in the open or in the recess or cavity in which the negative end of the blade revolves, stationary guide blades may be fitted around the said negative end, and, if required, these guide blades may be attached to the inner circumference of the recess or the exteriorof the side Wall ofthe casing.

, which &

-The said guide blades may be arranged in radial planes or obliquely thereto, and may be oblique tothe axis of the fan, or at some suitable deflecting angle. I findv that guide blades disposed at an an le of 30 to the plane-of rotation and lea ing in the direction of rotation give good results. In some cases another series of fixed guide blades. may be employed aroundthe fan wheel, on the positive side of the said partition to suitably engage and guide the air which is being discharged, or even to gulde and divert the flow of air in a suitable direction when my invention is applied to compounding in series.

In the arrangement indicated in Fig. 7 the part of the recess toward the positive end of the fan wheel is somewhat increased .in diameter as compared with the previous illustrations so that there is a considerable space between the most contractedportion and the periphery of the fan wheel. In this space is located the partitional device which consists'of guide blades 9 which may be placed obliquely to the axis and have openings between.

' In the arrangement indicated in F1g.-8

. that portion of the casing Y which forms the eye is now continued toward the back end. The opening of the eye is now most contracted in the neighborhood of the neutral point and the eye Y may be furnished with guide blades g, which may be straight as H1 Fig. 20, .although it is not essential that they should be straight, as a curved form is operative, and may be employed. The blades are preferably oblique to the, axis as in Fig. 20. In the arrangement of Fig. 8 itwill be seen that thecasing is no longer a pary tition in the same sense as in Fig. 6 and the fan may be.said to rotate in a duct Y of larger diameter than the fan, the air being drawn in at one end and discharged at the other. It may have the form of a double cone instead of a curve as shown in Fig; 8, I and this double cone may be combined with; a partition. From the above illustrations it will be ob-, vious that the principle of my invention may be applied inwidely difierent ways, so long as it is arranged that the'air which feeds the negative end of the blades comes mainlyfrom the suction side of thefan and is not taken by recirculation back from the air ha already passed throughfthe'positive porztibn of the blades. 'It will further Qbe obse ved that my invention leads to the important development in which the air drawn in axially into thefan wheel is combined with air drawn in through the negative ends ofthe blades and also with air drawn in around the periphery of the blades without passing through the blades at all. The result of such anarrangement is that the frictional loss due to high velocity of .eter of fan wheel which will deal with a given volume of air will also be considerably reduced.

It is obvious that my improvements may be applled either with or without a casing, according to the conditio 1S pertaining to the employment and location of the 'fan wheel, provided that the fluid to be operated on by the negativepart or parts of the fan Wheel be separated from that which discharges from the positive part thereof, in accordance with the principles hereinbefore lndicated. In the arrangement shown in F 1g. 8 the fan wheels may be'regarded as being placed in a space which forms a term contracto; and some of the improved results whlch arise from this form may be regarded as flowing from the combination of a fan wheel with an inclosed space in the form of a uena cmtmcta, The cavity or recess into which the negative end of the fan projects may in some cases be eccentrically disposed or may be of spiral form, and the wall or 9 able inclosing casing, that the air discharged from the positive end of the first fan wheel may enter the negative end of the second,

and so on, whereby an in creasedpressure is obtained in they discharge from the last wheel in the series. The casing wherein said fan wheels operate may be provided with suitable partitions or fixed guide blades fulfilling the office thereof or with suitable contracted portions, with'or without fixed gulde blades. A suitable intermediate space or chamber with or without suitable guide blades is provided between the closed back of the first fan wheel, and the open intake end of the succeeding one, wherebythe air discharged from the positive part of the first fan wheel is guided to the negative part and intake opening of the intakeend of the succeeding fan wheel, and so on.

Figs. 4, 5, 6, 7 and 8 may be said to represent diagrammatically either a wall fan or an incased fan. In constructing a wall fan according to this invention the inclosing frame or the aperture in the wall will be constructed to embody the features .men-

.length of the fan blades.

casing may spring from that part of the eye.

which is of smallest diameter or where the eye joins the end of the guide blades which projects toward the discharge end, or the casing may spring from the. inner end of a duct such as Y Y Fig. 8, constructed as described, and inclosing more or less of the The casing may be of the usual snail-shaped type or that part of the casing which extends over the positive part of the blades may be of cylindrical form suitably enlarged or flared outward over the positive end of thefan, and

adapted to deliver tlie air into a delivery portion of the casing disposed alongside at the back end of the fan, said delivery part of the casing being either cylindrical, snailshaped, or other suitable shape, as may be selected.

The drawings accompanying this specificationand numbered 9 to 29, show some furmodified arrangements of the guide blades.

In Fig. 10 which may be considered to be a plan of Fig. 9, g g are the guide blades on the negative side, and {7' g the guide blades on the positive side. The long arrowindicates the direction of rotation of the fan wheel. tion in which a partitional device consisting of three rows of guide blades of similar angularity are employed alternated one with the other, and without any partition such as Z, although the intermediate series gcorresponds with the position of the said partition Z. Fig. 12 shows in diagram a further modification, wherein in addition to the guide blades 9 outside the periphery of the wheel, guide blades 9 are provided extending axiallv along within the fan blades, and.

these guide blades 9 are illustrated as carried the full length of the blades but this length is not essential and they may if desired be made shorter than the full length of the blades. The said guide blades {7 may be either parallel to the axis or disposed at an angle" which may correspond with that of the guide blades 9. If required a closed drum-like casing may be provided within the inner edges of the guide blades 9 and this drum may extend part way inward or it may be carried substantially the full length of the blades. urther, if required,

Fig. 11 shows a further modifica-' the inner and outer guide blades 9 and 9 may be coupled "together or made in one piece at the intake end of the fan, as indi cated at 9*. The angular disposition of the guide blades 9 is shown in the developed plan view, Fig. 30. There the central drum m is employed the fan wheel may be said to rotate in an annular space with guideblades on the inner or outer sides, or both.

- Fig. 13 is a sectional elevation showing a wall fan where a fan wheel A is mountedso that its negative end rotates within an aperture 2 in a wall 3. The aperture 2 is considerably larger in diameter than the fan wheel A, so as to leave a suction space 2 between the sides of theaperture and the periphery of the negative end of the fan blades. The positive end of the fan wheel projects on the discharge side of the wall, and about mid-way between the ends of the blades, and, on the inner face of the wall3 is fitted a partition plate 2 dividing the space outside the periphery of the fan wheel,

and operating in the manner hereinbefore set forth. The positive ends of the blades discharge the air circumferentially outward between the partition 2 and a fixed shield plate 4:. The said plate 4 may if required be provided by an outward extension of the back plate of the fan wheel, instead of being fixed as shown. I

Fig. 14 shows a double intake fan wheel fitted to discharge air into a space 5 between the two walls 3, 3. The apertures in these walls may form the termination of two,

ducts or airways from a mine or building.

This construction need not be further de scribed as the parts are a duplication of those shown in Fig. 13, with the exception. that the plate 4 of said figure is omitted, both the positive portions a a of the double fan wheel A discharging into the space 5 between thewalls 3.

Figs. 15 and 16 show in cross-section and side elevation respectively a cased fan where the negative end I) of the fan wheel is mounted so as to rotate in a suction duct or eye 6 of considerably larger diameter than the periphery ofthe fan wheel, a partition Z being fitted in a similar manner to Fig. 13.

Inthis cased fan construction the air which is discharged from the positive end a of the fan wheel blades is discharged directly into the spiral volute of the casing 7, which casing is extended as shown axially beyond the back of the fan to provide the necessary area for the volume of air which is being discharged, the central part of the casing may be occupied by a recessed chamber 8.

Fig. 17 shows in sectional elevation one form of the cased fan made in accordance with my invention. In this construction the spiral or volute casing 7 is of ample dimensions for receiving and discharging the volume of air discharged from the positive end of the fan blades and has a fan wheel mounted therein in the usual manner. The suction duct or eye 6' is carried inward over the fan wheel to about the neutral point '0 the eye 6, the inner edge of these blades being suitably spaced away from the pcv with the air which has fan blades.

riphery of thefan wheel. The positive or discharging end a of the blades discharges into the casing 7 from which the air is delivered inthe usual manner. It will be seen in this construction that the wall of the eye 6 serves as'a partitioned device to divide the space outside the fan wheel so that the discharge from the positive portion a of the fan wheel is prevented from returning to the negative part b in the man her and for the purposes hereinbefore .set forth.

Figs. 18, 19 and 20 show a modified construction of single intake'wall fan applied as a mine fan, and where guide blades 9 are employed, and Fig. 21 is a sectional elevation showing a similar construction applied to a double intake mine fan. In these con-v structions as shown the partition Z is dispensed with, and the suction eye or duct 2 (Figs. 18 and 19) or ducts 2, 2 (Fig. 21) are fitted on their inner circumference with guide blades 9 g which operate in the man: ner before described; the said guide blades are disposed obliquely to the axis of the fan wheel as shown in Fig. 20, which shows a portion of the suction eye developed. The

guide blades? from, the' suction to the discharge side of the fan wheel without passing through the fan blades, as before described, and is discharged into the space 10 together passed'through the Fig. 22 shows a modified contr'uction in which a conical form of fan i employed mounted in a "conical aperture or duct which is sloped to conform with the conicity of the fan wheel, The walls of the aperture or duct may be parallel with the fan axis as in Fig. 23 instead of conical. The guide blades 9 are oblique to the axis of the fan wheel in Figs. 22, 23 and 24. l I

Fig. 23 shows a further modification wherein the fan wheelhas thepositivepart of conical shape. This construction may be modified to the extent that both the negative and the positive portions may be sloped at different angles, that is to say, while the negative portion can be-conical the positive half need not be parallel to the axis but may be more or' less sloped at a different angle to that of the negative portion. The fan wheel is shown as having the negative portion rotati'ng in an aperture, the walls of which are parallel to the fan axis, but the said walls may be made parallel to the negative po-rtion of the fan wheel as in Fig. 22. V

Fig. 24 shows a. wall type of fan applied to the ventilator of a ships stokehold, the fan wheel A being mounted directly on the shaft of a steam turbine, or other high speed prime mover, 10, .and disposed at the lower end of a ventilator 11. The construction is similar to Fig. 13, and the fan discharges the air all around in a horizontal direction over the ceiling of the roonf or hold 12.

Figs. 25 and 26 show in sectional elevation and side view a modified construction of FigQll, wherein guide blades is are disposed around the discharge from the positive ends of the blades. The said guide blades is may be flatas shown in Fig. 25 in hardlines, or

they may be curved, and they may be disposed tangentially, or at other suitable angle so as to promote the outward discharge of the air fromthe circumference of the fan. 4; is the annular shield plate already described with reference toFig. 13.

Figs. 27and 28 are respectively sectional. elevation and side views of a cased fan where guide blades 9 and g, are substituted as partitional devices for the partition Z.

In this construction that portion of the duct .2, in which the guide blades 9 are mounted covers the positive end of the fan blades, and is flared outwardly to deliver the air into one side of a spiral casing 7, which is entirely beyond the back end of the fan, and has a central recessed chamber 8 of the same diameter as the fan wheel or substantially so, and the dotted line 13 in Fig. 28 shows the outer circumference of the annular disf charge from the'fan wheel within the spiral casing. The guide blades 9, g are oblique to the axis substantially as in Fig. 20. i

The casings illustrated are only examples,

- and may be modified to suit requirements.

Fig. 29 shows in diagram one arrangement of the improved fan compounded or. arranged to work in series. A Aare the fan wheels spaced apart so as to provide an annular space ;0 betweenthem. The first fan A of the series is shown with guide blades 9, arranged oblique to the axis as in the construction hereinbefore described, and with out a partition Z (which may however .be employed if desired) while the second fan wheel A is provided with the partition Z a) parallel to the axis and the negative part b as in the construction hereinbefore described. The guide blades 9 of the second fan A are also obliquely arranged and are extended over the negative end of the fan blades and beyond the same toward fan A, and project inward at 9 so as to direct a portion of the air discharged from the fan the fan blades A. A fixed disk-like plate, p"

is mounted at the back of the first fan wheel A and supported from the casing spokes'and a drum 39 may be fixed thereon so as to be supported thereby and is carried forward into the intake chamber of the fan wheel A7. The drum p is shown as extending right up to the back plate of the fan wheel but this is not essential and it may extend for only half the length shown or part way. Guide blades such as 9 may be mounted at any suitable angle on the outer surface of the drum p but are preferably parallel with the axis. This construction is only to be taken as an example, and it is to be underpartially or substantially occupying axially the space between the back of the first or preceding fans of the series, and the negative end of the second or succeeding fan, and in their axial direction these blades may be fiat or curved with the concave of the curve facing the direction. of the air discharge from the first fan, while in their radial'direction they may be either curved or straight and set radially or at any suitable angle relative to a radial line and may be shaped so as to project intothe interior'of the sec- .ond or succeeding fan wheel.

WVith the compound fan the discharge areas from the second and succeeding fans should be so reduced in area as to allow only the discharge of sufficiently reduced volume to prevent the second or succeeding fan etting up a suction on the discharge of the p eceding or first fan and the blades of the second or succeeding fan wheel may have their axial length shortened relatively to that of the first orpreceding fan wheel in suitable pro portion to the increased pressure setup by For convenience of illustration, the drawings herein described show a fan wheel of the type described in my prior Patent No. 662895, but it is to be understood that other appended claims.

each succeeding wheel. I

types of fan wheel, such as hereinbefore referred to, may be substituted as preferred.

In the foregoing description of my invention and in the accompanying drawings, I have described and illustrated several equivalent constructions embodying my invention, 71. 6., a partition in its several forms shown, guide blades in the several constructions illustrated and the restricted aperture (as in Fig. 8), and by use of the term pan titional device in the claims, I mean to include all these forms in which my invention may be embodied, and other equivalent forms which may be substituted. It will therefore be seen that my invention is not limited to the constructions illustrated, although I have endeavored to illustrate the best mode'of constructing thesame known to me, but that other and equivalent devices maybe employed within the limits of the What I claim as my invention and desire to secure by Letters Patent is '1. In a centrifugal fan or pump, a fan wheel provided with blades, and a partitional device located relatively to the periphery of the fan wheel to substantially restrict the fluid which passes through centripetally or axially along the negative portion of the bladesto that which is mainly taken from the suction or intake side of the fan.

2. In a centrifugal fan or'pump, a fan' wheel provided with blades, the negative or ends of the blades being exposed to the space into which said air is circumferentially discharged, combined with means near said last named space to prevent the discharged air from returning to the space from which the air is drawn.

3. In a centrifugal fan or pump the combination of means which divide the space from which air is drawn from the space into which the air is discharged, a fan wheel so mounted in relation to said means that the negative ends of the. blades protrude into and are so exposed to the space from which the air is drawn into the fan that the air enters the fan wheel from said space both centripetally and axially while the positive ends of the blades are exposed to the space into which said air is circumferentially dis charged, said fan wheel and said dividing means being mounted in such relation that suflicient space is left around the periphery of the fan wheel for a portion of the air to pass by induction along the outside of the periphery from the suction to the discharge.

4. In a centrifugal fan or pump a fan wheel adapted to take in air axially and to discharge the sameperipherally in combinaaxis of the fan, said duct being of substan- I tially larger diameter than the fan Wheel and extending over the same from the suction to the discharge. I 6. A centrifugal fan or pump comprism a fan wheel in combination with a duct of larger diameter than the fan wheel, said fan wheel being adapted to rotate in said duct --and said duct being so shaped as to be of minimum diameter at or near the neutral part of the blades and whereby the air dealt with enters the one end of saidduct and is discharged at the other. 1

7. In a centrifugal fan or pump, the combination of a fan wheel, means for separating the space from which the air is drawn from the space into which it is discharged, comprising fixed guide blades located out- Side the periphery ofthe fan wheel so that a portion of the air dealt. with passesbetween said guide blades to the discharge side of the fan wheel as well as into and through the fan wheel.

8. In a centrifugal fan or pump, the combination of a fan wheel, means for separating the space from which the air is drawn from the space into which it is discharged,

comprising fixed guide blades angularly disposed and located outside the periphery of dealt with passes between said guide blades the fan wheel so that a portion of the air to the discharge side of the fan wheel as well as into and through the fan wheel.

9. In a centrifugal fan or pump, the com-' bination of a fan wheel provided with blades, means for separatingthe space from which the air is drawn from the space into which it is discharged, and fixed guide blades, tangentially disposed, and fitted around the periphery of the fan wheel out side the positive ends of the blades.

'-10.- In a centrifugal fan or pump, the combination with a fan wheel provided with blades, of means for admitting air to the said wheel both centripetally and axially, and means for separating the space from which the air is drawn from the space into which it is discharged, comprising. fixed guide. blades angularly disposed around the periphery of the fan wheel outside the positive ends of the fan wheel blades.

11. In a centrifugal fan or pump, the

combination witha fanwheel provided with blades, of a duct leading. from thespace from which air is drawn to the space into which air is discharged, a fan wheel adapted to rotate in said duct, said duct being of larger diameter than the fan wheel and having guide blades fitted on the inside and disposed obliquely relative to the axis, the

said duct, the guide blades thereon, and

that portion of the fan wheel which is concentrical with said duct all being of conical shape. I

12. In a centrifugal fan or pump, a fan wheel having a portion of conical shape combined with a duct, fitted on its inside with guide blades which have their inner edges sloped or shaped to follow the conicity of the fan wheel, and are obliquely disposed relative 'to the axis.

13. In a centrifugal fan or pump a casing into and through which the fan discharges,

'a fan wheel provided with blades and mounted in said casing, the negative end of said wheel protruding into the space' from which the air is drawn and exposed both peripherally and axially to said space so that the air from said space enters the fan wheel both axially and centripetally, the

positive ends of said blades projecting into and discharging peripherally into said casing;

14. In a centrifugal fan or pump the combination with a fan wheel provided with blades, of means for separating the space from which the air is drawn from the space into which the air is discharged, the negative ends of said fan wheel blades being ex posed to the space from which the air is drawn in such manner that the fan wheel'- is adapted to take in air both axially and centripetally, a casing inclosing the space into which the positive ends of the blades discharge, the positive ends of said blades means for separating the space from which the air is drawn from the space into which the air is discharged the negative portion of the fan wheel being exposed to or protruding into the space from which the air is drawn so that the fan wheel takes in air both centripetally and axially, a casing inclosing the space into which the positive ends of the blades discharge, said casing comprising a part concentric with the discharge end of the fan wheel and a spiral portion of the casing into which said concentric portion is adapted to discharge.

16. In a centrifugal fan or pump the combination with a fan wheel provided with blades, of means for separating the space from which the air is drawn from the space into which the air is discharged, said separating means being so located in relation to said fan wheel that the negative ends of the fan wheel blades are exposed to the space from which the air is drawn in such manner that the fan wheel takes in, air both axially and centripetally and discharges the same circumferentially from the positive end of the blades, and fixed guide blades disposed within the inner radius of the fan wheel blades.

17. In a centrifugal fan or pump the combination with a fan wheel provided with blades, of means for separating the space from which the air is drawn from the space into which the air is discharged, said separating means being so located in relation to said fan wheel that the negative ends of the fan wheel blades are exposed to the space from which the air is drawn in such manner that the fan wheel takes in air both axially and centripetally and discharges the same circumferentially from the positive end of the blades, fixed guide blades disposed within the inner radius of the fan wheel and fixed guide blades referably disposed at a suitable angle and fitted outside the periphery of the fan wheel blades.

18. In a centrifugal fan or pump the combination with a fan wheel provided with blades, of means for separating the space from which the air is drawn from the space into which the air is discharged, said separating means being so located in relation to said fan wheel that the negative ends of the fan wheel blades are exposed to the space from which the air is drawn in such manner that the fan wheel takes in air both axially and centripetally and discharges the same circumferentially from the positive end of the blades, fixed guide blades disposed Within the inner radius of the fan wheel, a closed drum-like casing of much less diameter than the inner circumference of the blades and disposed within the intake cham-,

.fan wheel blades are exposed to the space from which the air is drawn in such manner that the fan wheel takes in airboth axially and centripetally and discharges the same circumferentially from the positive ends of the blades, fixed guide'blades disposed within the inner radius of the fan wheel and fixed guide blades preferably disposed at a suitable angle and fitted outside the periphery of the fan wheel blades, a

closed drum-like casing of much less diameter than the inner circumference of the blades and-disposed within the intake chamber of the'fan wheel.

20. In a centrifugal fan or pump, a fan wheel having axially extending blades adapted to rotate in an annular path, inclosed by an open-ended annular duct, a substantial space being provided between the inner walls of said duct, and the outer edges of said blades, fixed guide blades attached to the inner faces of said duct and disposed outside of the outer circumference of the annular path of said fan blades with a clearance space between said fixed guide blades and the fan blades, and a drum within said fan Wheel and located in the intake chamber.

21. In a centrifugal fan or pump, a plurality of fan wheels compounded in series, i

an inlet eye to the first fan of the series of wheel whereby the negative end of said first fan wheel is exposed both peripherally and axially to the said eye and is adapted to take in air both axially and centripetally, an intermediate chamber into which the positive end of the first fan wheel discharges, the second fan Wheel having its negative end rotating in an eye or duct of larger diameter than the periphery of the fan wheel and whereby the saidnegative end of the fan wheel is exposed both axially and peripherally to said 'eye or duct and the intermediate chamber, a discharge duct or easing into which the positive end of the final fan of the series discharges and means Whereb the air discharged from the positive end 0 any one fan is prevented from returning to the negative end of the same fan.

22-. In a centrifugal fan or pump, a plurality of fan wheels compounded in series, an inlet eye to the first fan of the series of substantially larger diameter than the fan wheel whereby the negative end of said first fan Wheel is exposed both peripherally and axially to the said eye and is adapted to take in air both axially and centripetally, an intermediate chamber'into which the positive end of the first fan wheel discharges, the second fan wheel having its negative end rotating in an eye or duct of larger diameter than the periphery of the fan wheel and whereby the said negative end of the fan wheel is exposed both axially and peripherally to said eye or duct and the intermediate chamber, a discharge duct or casing into which the positive end of the final fan of the series discharges and means whereby the air discharged from the positive end of any one fan is prevented from returning to the negative end of the same fan, means whereby air may pass from the negative end of any one -fan wheel through the positive end thereof I rate by induction without passing through the fan wheel blades.

23. In a centrifugal fan or pump, a plurality of fan wheels compounded in SQIlGS,

an inlet eye to the first fan of theseries of I substantially larger diameter than the fan wheel whereby the negative end of said first fan wheel is exposed both peripherally and axially to the said eye. and is adapted to take in air both axially and centripetally, an intermediate chamber into which the positure in said partition being considerably larger than the fan wheel.

27. In a centrifugal fan or pump the combination with .a fan wheel provided with blades, of means for separating the space from which the air is drawn from the space K into which the air is discharged, the negative end of the'first fan wheel discharges,-

the second fan wheel having its negative end rotating in an eye or duct of larger diameter than the periphery of the fan wheel and whereby the said negative end of the fan wheel is exposed both axially and perlpherally to said eye or duct and the intermediate chamber, and a discharge duct or casing into which the positive end of the final fan of the series discharges and means whereby the air discharged from the positive end of any one fan is prevented from returning to the negative end of the same fan, a fixed drum disposed within the inner edges of the fan wheel blades of the second or succeeding fan, and guide blades disposed upon the periphery of said drum within the inner edges of the fan wheel blades.

tive ends of said fanwheel blades being exposed to the space from which the air is drawn in such manner that the fan wheel. is adapted to take in air both axially and centripetally, and by induction outside the periphery of the fan wheel, a casing inclosing the space into which the positive ends of the blades discharge, the positive'ends of said blades delivering air peripherally to said casing and said casing being adapted to col: lect and deliver the air in the required direction.

28. In a centrifugal fan or pump, a fan wheel having axially extending blades adapted to rotate in an annular path, and inclosed by an open-ended annular duct, a substantial space being provided between the inner walls of said duct, and the outer.

' edges of said blades, and having fixed guide blades attached to the inner faces of said duct and disposed outside the outer circumference of the annular path of said fan blades with a clearance space between said fixed guide blades and the fan blades, said guide blades so disposed relatively to the axis .as to substantially prevent the re-circulation of air discharged through the positive ends of said blades.

29. In a centrifugal fan or pump, a fan wheel having axially adapted to rotate in an annular path, and

"inclosed by an open ended annular duct, a

tive end thereof, whereby a greater pressure of air is obtained from the last of the series than the first.

25. In a centrifugal fan or pump, the combination with a fan wheel having blades and adapted to take in air axially of means disposed around the periphery of the fan wheel and adapted to isolate the air discharged from the positive end of the blades the negative end of the wheel being exposed both peripherally and axially to the space from which air is drawn into the fan whereby the said fan takes in air both axially and centripetally andinduces air to pass outside the periphery of the fan wheel from the suction to the discharge. without passing through the fan wheel blades.

26. In a centrifugal fan or pump, a fan wheel adapted'to take in air axially and to discharge the same peripherally, in combination with means whereby the space around the periphery of the fan-wheel is divided consisting of a partition located near the neutral part of the blades, the apersubstantial space being provided between the inner walls of said duct, and the outer extending blades edges of said blades, and having fixed ra- .dial guide blades attached to the inner faces of said ductand disposed outside and inside the outer andinner circumferenceof the annular path of said fan blades with a clearance space between said fixed guide blades and the fan blades.

30. In a centrifugal fan or pump, a plurality of fan wheels compounded in series,

.an inlet eye to the first fan ofthe series of substantially larger diameter than the fan wheel whereby the negative end of said first fan wheel isexposed both peripherally and axially to the said eye and is adapted to take in air both axially and centripetally, an. in-

termediate chamber into which the positive end of thefirst fan wheel discharges, the

second fan wheel .having its negative end rotating in an eye or duct of larger diameter than the periphery of the fan wheel and whereby the said'negative end of the fan wheel is disposed both axially and peripherally to said eye or duct and the intermediate chamber, and a discharge duct or casing into which the positive end of the final fan of the series discharges and means whereby the air discharged from the positive end of any one' fan is prevented from returning to the negative end of the same fan, a fixed drum disposed within the inner edges of thefan wheel blades of the second orsucceeding fan.

31. In a centrifugal fan or pump, the combination with a fan wheel having blades and adapted to takein air axially of means disposed around the periphery of the fan wheel. and adapted to isolate the air dis-' ative to the periphery of the fan wheel, for

opposing the passage of air discharged at the positive part of the blades to the negative part of said blades.

83. In a centrifugal fan or pump, a fan wheel, and a partitional device located relative to the periphery of the fan wheel, for

, obstructing the circulation of air discharged at the positive part of the blades to the negative part of the blades.

3i. In a centrifugal fan or pump, a fan wheel having axially extending blades adapted to rotate in an annular path inclosed by anopen-ended annular duct, a substantial space being provided between the inner wall of said duct and the outer edges of said blades, fixed guide blades attached to the inner faces of said duct, and a clearance space being provided between said fan blades and said guide blades, said guide blades so disposed relative to the axis as to substantially prevent the re-circulation'ofi air discharged through the positive ends of said blades. 7

35. In a centrifugal fan or pump, a fan wheel having axially extending blades adapted to rotate in an annular path inclosed by an open-ended annular duct, a substantial space being provided between the inner wall of said duct andthe outer edges of said blades, fixed "guide blades attached to the inner faces of said duct, and inclined relative to the axis, and a clearance space being provided between said fan blades and said guide blades.

36. In a centrifugal fan or pump, a plurality of fan wheels compoundedin series, each of said wheels having axially extending blades adapted to rotate in an annular path inclosed by an open-ended annular duct, a substantial space being provided between the inner wall of said duct and the outer edges of said blades, fixed guide blades attached to the inner faces of said duct and inclined and centripetally and discharges the same relative to the axis, a partition having a diameter substantially equal to the first fan wheel between said wheels, and a clearance space being provided between said fan blades and said guide blades.

37. In a centrifugal fan'or pump, a plu- ,rality of fan wheels compounded in series,

each of said wheels having axially extending blades adapted to rotate in an annular path inclosed by an open-ended annular duct, a substantial space being provided between the inner wall of said duct and the outer edges of said blades, fixed guide blades attached to the inner faces of said duct and inclined relative to the axis, a partition having a diameter substantially equal to the first fan wheel between said wheels, and a drum extending within the second wheel, and a clearance space being'provided between said fan blades and said guide blades.

38. In a centrifugal fan or pump, the combination with a fan wheel provided with blades of means for separating the space from which the air is drawn from the space into which the air is discharged, said separating means being so located .in relation iLQ said fan wheel that the negative ends of the fan wheel blades are exposed to the space from which the air is drawn in such manner that the fan wheel takes in air both axially and centripetally and discharges the same circumferentiallyfroin the positive ends of the blades, and fixed guide blades disposed within the inner radius of the fan wheel blades, and substantially parallel to the fan wheel axis.

' 39. In a centrifugal fan or pump, the combination with a fan wheel provided withn blades of means for separating the space fromwhich the air is drawn from the space into which the air is discharged, said separating means being so located in relation to said fan wheel that the negative ends of the fan wheel blades are exposed to the space from which the air is drawn in such manner that the fan Wheel takes in air both axially and centripetally and discharges the same circumferentially from the positive ends of the blades, and fixed guide blades disposed within the inner radius of the fan wheel blades, and substantially parallel to the fan wheel axis, and extending to about midway of the axial length of the blades.

40. In a centrifugal fan or pump, the combination with a fan wheel provided with blades of means for separating the space from which the air is drawn from the space into which the air is discharged, said sepa rating means being so located in relation to said fan wheel that the negative-ends of the fan wheel blades are exposed to the space from which the air is drawn in such manner that the fan wheel takes in air both axially circumferentially from the positive ends of the blades, fixed guide blades disposed within the inner radius of the fan wheel blades and substantially parallel to the, fan wheel axis and extending to about midway of the axial length of'the blades, and fixed guide blades. preferably disposed vat a suitable.

angle and fitted outside the periphery of the fan wheel blades.

41. In a centrifugal fan or pump, a fan wheel having blades, and a partitional device located relative to the periphery of the fan wheel for opposing the recirculation of fluid discharged through the positive ends of said blades to the negative ends thereof.

42. A centrifugal fan or pump having a multi-bladed rotor, the negative ends of the blades being exposed to the space from which the air is drawn and a partitional device located relative to the periphery of the fan wheel for opposing the re-circulation of ,fluid discharged through the positive ends of said blades to the negative ends thereof. 43. In a centrifugal fan'or pump, a fan wheel having blades, a partitional device lo- -cated relative to the periphery of the fan Wheel and adapted to substantially 'guide over and inclosing the positive parts of the blades and having portions terminating near the neutral parts of the blades, the negative end of said wheel protruding into the vspace from which the air is drawn and exposed both peripherally and. axially to said space, and said negative end adapted to draw air into the fan wheel both axially and cen tripetally, 'the positive ends of said blades discharging peripherally into said casing.

' 45. In a centrifugal fan or pump, a casing into and-through which the fan discharges, a fan Wheel provided with blades and mounted in said casing, the casing extending over and inclosing the positive parts of the blades and having a portion terminating near the nuteral parts of the blades and spaced apart from the periphery of the wheel, whereby a space is provided for the passage of air into the casing without passing through the wheel, the negative ends of said blades protruding into the space from peripherally and axially to said space, and saidnegative end adapted to draw air into the fan wheel both axially and centripetally, the positive ends of said blades discharging peripherally into said casing.

In witness whereof, I have hereunto signed my name in the presence of two subscribing witnesses.

SAMUEL OLELAND DAVIDSON.

. Witnesses: JOHN JOHNSON, -HUGH TAYLOR COULTER.-

..which the air is drawn and exposed both 

